When the coefficient of an unknown number in the two equations of a system of linear equations of two variables______ Or_________ Or___________ The method of addition, subtraction and elimination is often used

When the coefficient of an unknown number in the two equations of a system of linear equations of two variables______ Or_________ Or___________ The method of addition, subtraction and elimination is often used

When the coefficients (equal) or (opposite) or (integral multiple) of an unknown number in two equations of binary linear equations, the method of addition, subtraction and elimination is often used

Evaluation problem does not require simplification. The unknown number directly with the number line

Yes, but it's easier to miscalculate

For an equation with two unknowns, what is the basis for the equation to hold after the position of the two unknowns is changed?
For example (1-x) / (1 + x) = t (x is not equal to - 1), then x = (1-T) / (1 + T) (t is not equal to - 1)
The original topic comes from the innovative design guidance case of Shaanxi people's publishing house, the mathematics compulsory training of North Normal University Edition, p80, question 6 (2)

This is just a coincidence